Conventionally, electronic devices having a waterproof structure, such as a watch and a mobile phone, are used. For example, a push-button switch of an electronic device having a waterproof structure as in Patent Document 1 has a fixed structure portion, and an operation body attached to the fixed structure portion so as to be able to advance and retract with respect to the fixed structure portion. The operation body is provided with a sliding portion configured to be slidable with respect to the fixed structure portion, and an operation head connected to the outside of the sliding portion, shaped to overhang the sliding portion, and having a larger diameter than the sliding portion. An elastic member capable of being elastically deformed is held between the overhang portion of the operation head and the fixed structure portion. The elastic member has a cylindrical shape surrounding the sliding portion. The elastic member has a first contact portion that is in contact with the inner surface of the overhang portion of the operation head, a second contact portion that is in contact with a portion facing the overhang portion in the fixed structure portion, and a third contact portion that is in contact with the sliding portion.